Oil cooler control



Feb. 18, 1947. J KEMPER OIL COOLER CONTROL Filed Feb. 6, 1943 Brmantor 3 Patented Feb. 18, 1947 UNITED STAT-ES PATFZT GFFICE OIL COOLER CONTROL James M. Kemper, Hollywood,

Calif., assignor to The Garrett Corporation, Airesearch Manufacturing Company,

division,

Los Angeles,

" means for devices wherein the heat content of a medium, such as oii, for example, is changed by transmission of heat from one area to another.

Although the invention is of general utility as a control for heat transmitting devices, it is of especial utility with oil coolers of the type employed to change the heat content of the lubricating oil employed in aircraft engines; therefore, the invention will be explained in detail with reference to this preferred use of the invention.

It is an object of the invention to provide a control device which will operate with a minimum of hunting. This term, as used herein, means that condition in a control device wherein the control part, such as a valve, is constantly moving back and forth as though seeking or hunting for a place of rest. The rate of heat dissipation in an oil cooler depends upon a number of factors, one of which is the velocity or quantity of air flow through the air tubes of the cooler. It is a function of control devices used with coolers to vary the air flow as the heat absorbing requirements of the cooler change. That isto say, if the oil issuing from the cooler is at too low a temperature, due to the fact that too much heat is being extracted from the oil as it passes through the cooler, the air fiow is diminished, or, on the other hand, if the temperature of the oil issuing from the cooler increases above a predetermined value, it is a function of the oil cooler control to increase the flow of air through the air tubes of the cooler. A change in the air flow does not produce an immediate change in the temperature of the oil due to an inherent lag in. the characteristics of the cooler resulting from the fact that the dissipation of heat from the oil in the shell is not directly to the air, but consists first in absorption of heat from the cooler tubes by the air so that the metal walls of these tubes will then have capacity for absorption of heat from the oil. This lag results in the effect called hunting,

It is an object of the present invention to provide an oil cooler control having a simple means for producing periods of rest in the action of the control to compensate for the lag in the response of the cooler to changes in air flow, thereby minimizing the hunting action of the control.

It is a further object of the invention to provide an oil cooler control in which the movement of the air controlling element in response to a change in temperature of the oil corresponds relatively closely to'the change in air flow required to offset the increase in temperature of the oil.

It is an object of the invention to provide a control for a device for changing the heat content of a medium, which device has means to vary the action of the means for changing the heat content of the medium, which is under control of a thermostat and associated switch parts which are given relative movement by the thermostat and which are provided with an additional relative movement of reciprocating character so that these switch parts will. be periodically disengaged even though the condition of the thermostat due to its temperature received from the medium might be such as to normally hold the switch parts in engagement.

A further object of the invention is to provide a device of the character set forth in the preceding paragraph wherein one of the switch parts is moved back and forth by the thermostat in accordance with temperature changes, and the other of the switch parts is moved continuously with a reciprocating motion through a prescribed range of movement.

A further object of the invention is to provide a control device having a switchpart movable in opposite directions from a central position so as to engage contacts disposed on opposite sides thereof, and cam means for reciprocating these laterally disposed contacts.

Further objects and advantages of the invention will be brought out in' the following-part of the specification.

Referring to the drawing which is for illustrative purposes only,

Fig. 1 is a schematic view showing an.embodiment of my invention.

Fig. 2 is a fragmentary sectional view showing the manner in which the control unit may be applied to a heat changing device, specifically an oil cooler.

Fig. 3 is a view looking toward the left end of Fig. 2.

In Fig. 2 I have shown a heat changing device iii which is in fact an oil cooler having a shell H with an inlet 12 through which oil passes as indicated by arrows l3 and an outlet !4 through which the cooled oil makes its exit as indicated by arrows l5. Within the shell ii there are tubes 16 forming a part of the heat varying means of the device I0. A fluid having capacity for heat is passed through these tubes l6. Such fluiclfiin an oil cooler is preferably air. Whether thejoil which engages the tubes I6 is heated or cooled will depend upon the relative temperature of the acraaor air which passes through the tubes iii. In other words, the change in the heat content of the medium comprising the oil depends upon whether air which passes through the tubes i6 is hotter or cooler than the oil which is brought into con= tact with the external surfaces of the tubes while passing through the interior of the shell M. It

is of course a function of the oil cooler to reduce the temperature of the oil which passes therethrough, but it will be recognized that the control means to be hereinafter described will function with a heat changing device adapted to either increase the heat content of a medium or to decrease the heat content thereof.

From the outlet it the oil passes into a casing I? wherein a portion of the oil is brought into contact with a thermostat i8 comprising a helix of bimetallic thermostat stock having its free end BB9 connected to a rotatable shaft. having a switch part 2! connected to its outer end.-

A supporting plate 22 is disposed in a position to be traversed by the switch member 2! Switch parts 23, specifically designated as switch parts 23a and 23?), are disposed on opposite sides of the swinging portion of the switch part 28 and are supported for swinging movement on pins 24 surrounded by insulator bushings 25. Springs 26 urge the switch parts toward a cam 27 which is supported on a shaft 28 which is rotated at relatively slow speed by motor means which may consist of a small motor 2% and a reducing gear 3il, details of which are not shown for the reason that motors with built in reducing gears are old and well known in the various mechanical arts. v The switch parts 2i and 23 are shown as simple electrical contacts. Relative movement of these switch parts is produced by the thermostat l8, and a second relative movement thereof is produced by the cam 27. When the oil engaging the thermostat I8 is at a predetermined or normal temperature, the switch contact 2! will be held in a centralized position as shown in Fig. 1. As

the cam 27 rotates, the contacts 23:: and 23b will be reciprocated through limited arcs of movement on opposite sides of the contact 2i, but

will not engage the contact when it is in the centralized position referred to. For example, the contact 23a in Fig. l is shown in the extreme position thereof permitted by the cam 27. When thecam 21 rotates through an arc of 180, the switch contact 23a will be moved leftward and the switch contact 23b will move into the posi tion thereof shown by dotted lines 23. It will be seen, accordingly, that the contacts 28 will be constantly reciprocated back and forth between positions close to the centralized position of the contact 2! and positions remote from the centralized position of the contact 2!, and that should the contact 26 be swung from its centralized position, it will be intermittently engaged by the contact 2341 and the contact 23b, depending upon the direction in which the contact 2i is moved from its centralized position. For example, should the oil which engages the thermostat it drop in temperature, which drop is an indication that too much heat is being removed during the passage of the oil through the cooler,

- the thermostat l8 will swing the contact 26 leftward into a position such as shown in Fig. 3 wherein it may be engaged by the contact 230:. The length of time that the contact 2i will remain in engagement with the contact 23a; depends upon the distance it is swung from central ized position, and this distance will correspond to or be a measure of the drop in the oil tern stopping the motor when the perature from the prescribed normal value for which the control is set. For example, the cam 27 is in continuous clockwise rotation, as indicated in Fig. 3, and as the leading slope 3i of the cam 27 passes under the cam follower 32 of the contact 23a, the contact 23a will engage the contact 2! at the position of the cam 27 shown inFig. 3. The contact 23a will remain in contact with the part 2i during the period of time required for the cam 21 to bring the following or lifting slope 33 of the cam into engagement with the follower 32 so as to lift the contact 2302 from engagementwith the contact 25. If there is only a, slight deflection of the contact 2! from its centralized position, the period of engagement of the contact 23a therewith may endure for several seconds only, but, should there be a large deflection of the switch contact 2i, its period of engagement with the contact 23a may continue through ten or twenty seconds.

As shown inFig. 1, the contact 2! is connected through a switch 56 with a ground 35 so as to be electrically connected to a power source indicated as a ground battery 36. Should the contact 2i engage the contact 23a, a relay 3? will be energized through a conductor 38. This relay 3? embraces a motor switch 39 which will be then closed so as to energize a winding 40 of a reversible motor ii, shown in a power circuit 32 including a battery it. The energization of the windin as drives the mot-or ll in clockwise direction so as to swing a lever M which is connected through a link t5 with a shutter or valve mechanism it, to actuate the same toward open position. In a similar manner, should the contact 2i be moved rightward from its centralized position, so as to be engaged by the contact 231), a relay Q? will be energized through the conductor 18 and the switch 459 of the relay 61 will be closed so as to cause a flow of current through a conductor 50 and the reverse field winding 58 of the reversible motor ll, to operate the motor ill in counterclockwise direction whereby opening movement will be transmitted through the link G5 to the shutter or valve mechanism 36. Limit switches 52 and 53 are provided in circuit with the field windings (l6 and 5! to stop the motor ti When it has moved the lever 843 into either of its extreme positions. I The limit switches 52 and 53 gaged by the lever 'M as it moves into its extreme position. The switch 56 is connected with an override means associated with the relay 31. To move the switch 56 upward from the position in which it is shown in Fig. 1, there is a piston 57 which moves in a cylinder 58 connected through a duct 59 with the inlet; portion of the cooler so that when excess pressure builds up in the cooler, the piston 411 will move the switch 56 upward so as to engage the contact at the lower end of the conductor 56, thereby energizing the relay 3i and actuating the motor li so as to close the shutters it. The motor M will be operated in clockwise direction until the lift rod 56 is engaged and the switch 52 opened, so as to break the electric circuit through the field winding ll! of the motor, which is at this time energized, thereby shutters t6 reach closed position.

A feature of the invention is that the control provides definite periods of rest in the operation of the motor means which opens and closes the shutters, thereby allowing time for the cooler to respond to the change in the shutter position, which has been efiectuated by a motor operation.

i shutters: 46 to compensate for the fault in the temperature of the oil which has caused the ther= mostat Hi to move the switch member 2! from its centralized position. A period of time will elapse beforejthe cam 21 has made a complete revolution and during this period of time, the change in the shutter position may have eifected a change in the temperature of the oil to correct the fault and to return the thermostat switch contact 2! to its centralized position. On the other hand,

the change in the shutter position may not have I been sufflcient to correct the fault in the oil temperature, with the result that upon the succeeding revolution of the cam 21, the reciprocating switch contact will again engage the contact 2| to produce a further small actuation of the motor 4| to further move the shutters 46. In this way, a constant excess hunting movement'oi the shuttem is avoided.

If there is a small change in the is a corresponding new position of adjustment of i l the shutters 46 to compensate for this change in oil temperature, In previous controls with which the applicant is familiar, the action 01 the thermostat does not produce this exact adjustment of the shutters to compensate for a particular change in oil temperature, but will cause the shutters to move far beyond the proper position thereof. In other words, the action of the thermostat is ordinarily to over-compensate so that the shutters are kept constantly moving toward opened and then closed positions. In the present invention the introduction of the period of delay in the operation of the control substantially avoids this over-compensation and therefore maintains the oil which leaves the cooler at a temperature very close to a value for which the control is set. I

I claim as my invention: 1

In a control for an oil cooler having means for temperature I of the oil from a prescribed normal value, there a n it? upon each revolution; an operative connection between said switch parts and said motor means whereby changes from the predetermined temperature will impart movement to the first switch part for cooperative engagement with the secend or third switch parts thereby effecting operation of said motor means only while said second or third switch parts are in engagement with i the cam means thus eiiecting a like partial adjustment of the shutter means, said operative- I connection comprising a source of electric current connected to said first switch part, a first conductor connected to said second switch part for accomplishing ashutter-closing operation of said motor when said second switch part engages said first switch part, and a second conductor.

. operating in response to a rise in pressure in said cooler to disconnect said source of electric current from said first switch part and connectsaid source of electric current tosaid first con- I ductor so as to accomplish a. shutter-closing operbringing the oil into heat exchange relation to a flow of cooling medium, the combination of: partially adjustable shutter means operable to vary the flow of said cooling medium; periodically operable motor means to actuate said shutter means toward open position or toward closed position; a thermostat exposed to changes in temperature of said oil; a. switch part moved back and forth from a central position of predetermined temperature by said thermostat: a second switch part disposed in a position to be engaged by said first switch part when it is moved in one direction from said central posi tion; a third switch part disposed so as to be engaged by said first switch part when it is moved in another direction from said central position; continuously rotatable means between said sec-- 0nd and third switch parts having means to eiIect reciprocation oi the second and third switch parts alternately toward said first switch part at ion of said motor.

JAMES M. KEIVIPER.

sessions orrnn The following references are of record in the file or this patent:

UNITED STATES PATENTS Number Name Date 479,849 Shepherd Aug. 2, 1892 1,420,838 Swift June 20, 1922 2,019,945 Wells Nov. 5, 1935 Re. 21,777 Kimball Apr. 22, 1941 1,743,545 Helpbringer Jan. 14. 1930 1,979,810 Petersen Nov. 6, 1934 2,209,566 l-lcrnung July 30, 1940 2,220,028 Smith Oct. 29, 1940 2,291,607 Chausson Aug. 4, 1942 1,420,349 Swift June 20, 1922 1,835,307 Johnson Dec. 8, 1931 2,314,937 Harmon Mar. 30, 1943 2,333,066 Yeida Oct. 26, 1943 2,348,212 Gill May 9, 1944 2,134,257 Leutwiler Oct. 25, 1938 1,835,907 Shiland Dec. 8, 1931 2,029,159 Bear Jan. 28, 1936 2,108,601 Leutwiier Feb. 15, 1938 FOREIGN PATENTS Number Country Date Apr.18,1942 esipee British Filed {Sept 12, 1938 0% REFERENCES Fairchild, pages 305 and 317 oi! article entitled l lote on the Throttling of Electric Hea by C. Owen Fairchild in Instruments Magazine, Decernber 1937, published by The Instruments Pub- 4,. iishing 00., Pittsburgh, Pa.

(Certificate of Qorreetiem Patent No. 2,416,261. February 18, 1947 JAMES M. KEMPER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 6, line 37, for the number 1,420,838 read 1,420,348; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 6th day of May, A. D. 1947.

LESLIE FREE,

First Assistant Uommissipner of Patents. 

